I have set up the following problem so you will have a chance to do it before seeing the answers and how the answers are calculated.

Check your answer...do you agree? Great if you do. If you do not check the Solution: below the table to see how the number of molecules of H₂SO₄is calculated.

Formula

M , Molar Mass

(gmol^-1)

mass of sample

(g)

n, number of

moles of sample

N, number of atoms,

molecules or formula units

H₂SO₄

98.0

0.825 0.00842

5.07x 10²¹ molecules

Solution:

We are to calculate the number of molecules in the sample. How do we know we calculating molecules, rather than atoms or formula units? Since H₂SO₄ is a covalent compound it exists as molecules at the atomic level. To convert from moles to molecules we need to use Avogadro's number.

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Check your answer...do you agree? Great if you do. If you do not check the Solution: below the table to see how the number of molecules of H2SO4 is calculated.

Formula

M , Molar Mass

(g­mol-1)

mass of sample

(g)

n, number of

moles of sample

N, number of atoms,

molecules or formula units

H2SO4

98.0

0.825

0.00842

5.07x 1021 molecules

Solution:

We are to calculate the number of molecules in the sample. How do we know we calculating molecules, rather than atoms or formula units? Since H2SO4 is a covalent compound it exists as molecules at the atomic level. To convert from moles to molecules we need to use Avogadro's number.

Click here if you'd like to try another problem.

Check your answer...do you agree? Great if you do. If you do not check the Solution: below the table to see how the number of molecules of H₂SO₄is calculated.

(gmol^-1)

H₂SO₄

5.07x 10²¹ molecules

We are to calculate the number of molecules in the sample. How do we know we calculating molecules, rather than atoms or formula units? Since H₂SO₄ is a covalent compound it exists as molecules at the atomic level. To convert from moles to molecules we need to use Avogadro's number.